There are many instances when it is desirable or necessary to manufacture snow so as to enable the use of ski facilities, for example, or to improve snow conditions at such facilities. Snow making equipment presently is available and generally is of two kinds. One makes use of compressed air to nucleate seeding ice crystals which then are mixed with water droplets within an aerosol or air stream of sufficiently low ambient temperature to make acceptable snow. The other kind of snow making equipment is a so-called airless snow making machine. The term "airless" is used to indicate the complete absence of compressed air as a nucleating agent. The apparatus disclosed herein relates to an airless machine for making snow.
The only known commercially available, truly airless snow making machine is that disclosed in Ericson et al U.S. Pat. No. 3,610,527 issued Oct. 5, 1971. The Ericson et al airless snow making apparatus discharges water onto the blades of a rotating fan adjacent its hub. The water spreads over the blades in a thin film the surface of which is subjected to evaporative cooling, thereby chilling the water. The majority of the water, however, passes over the trailing edges of the blades and is atomized as it enters the aerosol.
The known prior art airless apparatus also utilizes a fan having alternate blades of different lengths for the purpose of producing less recirculation of the aerosol at the blade tips. The effect of the reduced circulation is to increase the throw of the aerosol or, stated differently, the distance over which frozen water particles can remain entrained in the aerosol. The lower recirculation is attributed to the counteracting influence of one blade tip vortex on another. However, at higher ambient temperatures the lower recirculation can create a "halo" containing wet droplets which circulate around the fan and result in a localized fallout or wet spot in the immediate vicinity of the machine. The wet spot can be minimized by reducing the water supply to the machine, but this also causes a reduction in snow production.
The apparatus disclosed in the Ericson et al patent has the leading edges of the longer set of blades located at a greater distance from the water supply than the shorter set of blades, so that the longer blades receive less water. As a result, a thinner film of water passes over the longer blades, thereby producing increased chilling of such water and providing a larger quantity of ice nuclei to seed the aerosol. One effect of this differential water distribution is icing of the longer set of blades at extremely cold ambient temperatures. Varying the distribution of water to provide more water for the longer blades reduces the icing of the blades, but it also reduces the ice nuclei thereby resulting in reduction in snow production at both higher and marginal ambient temperatures. Thus, the production of snow at both the upper and lower operating temperature ranges is limited by the particular proportion of differential water distribution adopted.
An object of the present invention is to provide snow making methods and apparatus which overcome or greatly minimize the disadvantages referred to above.